New renewable energy sources, including a solar cell, have been increasingly concerned recently as an alternative energy in terms of not using limited fossil fuel on earth and minimizing environmental contamination. However, the renewable energy sources have a problem in that it is difficult to stably supply power to loads, because voltage and current are unstable. Accordingly, a technology of stabilizing power output of a system, using an energy storage device such as a battery has been developed in recent years.
In the related art, renewable energy power generation systems had a structure supplying power from a plurality of power sources, using serial power converters. However, since the input power sources are independently provided, the battery charge may be different among the units. A charge balancing circuit (balancing circuit) independent from the power converters is used to prevent a difference in the battery charge.
As a method of balancing the battery charge, although there is a method of balancing battery charge by consuming power with resistors, the efficiency is low. Further, a method of balancing battery charge by using an inductor can increase efficiency, but it is required to additionally connect a power regulator to each of batteries, so the cost of a system increases.
The present invention is based on Korean Patent No. 10-1063057 (Aug. 31, 2011).